S334
Clinical - Breast
ESTRO 2026
Material/Methods: This retrospective study included patients treated with adjuvant hypofractionated radiotherapy according to the START-B regimen, using a three-dimensional conformal technique, between January and December 2023 at the Radiotherapy Department of Mohammed VI University Hospital in Tangier. The brachial plexus was delineated by the same radiation oncologist. The maximum dose (Dmax) was extracted from dose– volume histograms, with the constraint defined as Dmax < 45 Gy.Toxicity was assessed based on three parameters: neuropathic pain (Visual Analogue Scale, VAS), paresthesia (Common Terminology Criteria for Adverse Events, CTCAE), and functional limitation (Medical Research Council, MRC muscle strength scale). Patients with pre-existing rheumatologic or neurologic plexopathy were excluded.Statistical analyses (Spearman, Mann–Whitney U, and ROC curves) were performed using SPSS version 25.0. Results: A total of 90 patients were included, with a median age of 58 years (range, 35–80 years). All patients received neoadjuvant chemotherapy and surgery with axillary dissection: 44.4% underwent breast-conserving surgery and 55.6% radical mastectomy, followed by adjuvant radiotherapy.Neuropathic pain was reported in 15.6% of patients; 71% of cases were mild and 29% moderate according to the Visual Analogue Scale (VAS). Paresthesia of grade 1 (CTCAE) occurred in 42.2% of patients, and 8.9% experienced partial functional limitation.The mean time to symptom onset after radiotherapy was 28 months.The Dmax to the brachial plexus ranged from 0.24 to 57 Gy, with a median of 38 Gy and a mean of 30.7 Gy. It was significantly higher in patients who developed paresthesia, pain, or functional impairment (p < 0.001). No correlation was found with lymphedema (p = 0.95). Above 39 Gy, the risk of plexopathy became significant. Conclusion: Our study demonstrated that post-radiation brachial plexopathy is correlated with the Dmax received by the brachial plexus ,These findings highlight the importance of precise contouring, strict adherence to dosimetric constraints, and long-term clinical follow- up of patients. Keywords: Brachial plexus, Plexopathy
few studies in the literature have evaluated the setup margins (SM) around the clinical target volume (CTV) when using the VMAT technique. The objective of this study was to determine the SM based on image- guided positioning control (CBCT) in patients treated for breast cancer using VMAT. Material/Methods: This was a prospective dosimetric study including 10 patients treated for breast cancer with the VMAT technique. During radiotherapy, each patient underwent daily CBCT imaging prior to treatment delivery. Each CBCT was compared with the planning CT scan.Displacements (differences between CBCT and planning CT) were recorded along the lateral (x), vertical (y), and longitudinal (z) axes. Systematic ( ∑ setup) and random ( σ setup) errors were then determined. The setup margin was calculated using the Van Herk formula: 2.5 Σ setup + 0.7 σ setup. Calculations were performed using Microsoft Excel. Results: A total of 220 CBCT were realized during the treatment period. Systemic errors were 0,12 mm ; 0,16 mm and 0,2 mm in X,Y and Z axes respectively. Random errors were 0,42 mm ; 0,28 mm and 0,42 mm in X, Y and Z axes respectively. CTV to PTV margins were 0,6 mm ; 0,6 mm and 0,8 mm in the X, Y and Z axes respectively. Conclusion: In breast cancer radiotherapy planning with VMAT, the 5 mm margins routinely used in our practice for three- dimensional conformal irradiation appears to be
inadequate and should be increased. Keywords: breast, VMAT, setup margin
Digital Poster 4690
Hypofractionated Breast Radiotherapy : Does the Maximum Dose to the Brachial Plexus Determine the Risk of Plexopathy? Ibtissam touffahi, Abir outmani, hoda ibroun, wafae mersetti, soukaina morchid, nabila sellal Radiotherapy, Mohammed VI University Hospital, Tangier, Morocco Purpose/Objective: Breast cancer remains a major public health concern. Radiotherapy plays a crucial role in local control but can lead to toxicities such as radiation-induced brachial plexopathy. Although rare, this complication may cause severe sensory and motor deficits, significantly affecting patients’ quality of life.The objective of this study was to evaluate the correlation between the maximum dose received by the brachial plexus and the risk of post-radiation plexopathy in patients treated with hypofractionated breast radiotherapy.
Proffered Paper 4723
Is a boost to the tumour bed still indicated after breast-conserving surgery and whole-breast radiotherapy in the era of modern systemic therapy?
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